404 



APLACOPHORA 



H. 



Cryptoidea. — With double sutural laminae ; Crypto- 

 conchus^ Amicula, Qryptochiton, 



Fig. 266. — Neomenia 

 carinata Tullb. : a. 



Fig. 265. — Chitonellus fasciatus Quoy ; ant, anterior eud. 



I. Chltonelloidea. — Posterior valve funnel shaped ; lamina,e 

 thrown forward ; Chitonellus, Choneplax. 



Sub-order 2. Aplacophora. — Animal vermiform, foot 

 absent, or a mere groove, cuticle more or less 

 covered with spicules. 



According to Marion, one of the principal 

 authorities on the group, the Aplacophora 

 are perhaps Amphineura whose development 

 has been arrested at an early stage, their 

 worm-like exterior being ^ 



anus; gr, ventral ^^^q ^q adaptation tO SUr- 

 groove; m, mouth. n^i ^ 



roundings. Iney nave 

 hitherto been found chiefly in the N. Atlantic 

 and Mediterranean, generally at considerable 

 depths, and often associated with certain 

 polyps in a way which suggests a kind of 

 commensalism. 



Fam. 1. Neomeniidae. — Foot a narrow 

 groove, intestinal tube without differentiated 

 liver, kidneys with common exterior orilice, 

 sexes united, ctenidia present or absent. 

 Genera : Neomenia (Fig. 266), Paramenia, 

 Proneomenia, Ismenia, Lepidomenia, Bon- 

 der sia. 



Fam. 2. Chaetodermatidae. — Body cylindrical, no ventral 

 groove, liver a single sac, kidneys with separate orifices into the 

 branchial cloaca, two bipectinate ctenidia. Single genus, 

 Chaetoderma (Fig. 267). 



Fig. 267 .—Chaetoderma 

 nitidulum Lov. : a, 

 anus ; m, mouth. 

 X 3. 



Order II. Prosobranchiata 

 Visceral loop twisted into a figure of 8 (strep tone urous), right 



